Bug#906249: ,general: Long pause after lightdm login, gimp not starting except under strace

Linux 4.16 fixed CVE-2018-1108 by making the getrandom system call
(without GRND_NONBLOCK) block if insufficient entropy is available. This
causes applications to hang, and explains why mouse wiggling helps. As
Simon advised, we need individual reports for each application. I had to
build a custom patched kernel and use ltrace to identify the culpable
applications that affected me: